1. Field of the Invention
The present invention relates to an information conversion apparatus, an information conversion method, an information conversion program and a relay device.
2. Description of the Related Art
In recent years, in order to solve a shortage of IPv4 addresses, switching to IPv6 addresses has been proposed. However, in view of widespread network technologies and social penetrations, it is considered to be difficult to switch IPv4 addresses to IPv6 addresses at once and a configuration for using both of the IPv4 networks and IPv6 networks are being examined.
It is thus desired to smoothly perform communications between an IPv4 network and an IPv6 network.
Japanese Patent Application Laid-Open No. 2008-092607 describes a translator technology that establishes a communication between networks in different versions, which has different IP address application systems.
When a packet is transferred from an IPv6 network to an IPv4 network, the translator described in JP-A No. 2008-092607 extracts an IPv4 address from low-order 32 bits of an IPv6 address stored in a destination IP address field of an IPv6 packet and stores the address to a destination IP address field of an IPv4 packet.
Further, when a packet is transferred from the IPv4 network to the IPv6 network, the translator converts an IPv4 address stored in a transmitter IP address field of the IPv4 packet to an IPv6 address stored in the low-order 32 bits and stores the address to a transmitter IP address field of the IPv6 packet.
According to the technology described in JP-A No. 2008-092607, since IP addresses can be converted on Layer 3 (a network layer) of the OSI (Open Systems Interconnection) reference model, a communication between an IPv6 node and an IPv4 node can be realized.
However, it is difficult to realize communications between applications including IP addresses on Layer 7 (an application layer) of the OSI reference model. This is because the technology of JP-A No. 2008-092607 performs an address conversion regarding only IP headers on Layer 3 and may not convert address information written in IP payloads on Layer 7.
Further, JP-A No. 2007-104676 describes a technology related to a communication method for realizing a VoIP communication between a VoIP terminal based on IPv4 and a VoIP terminal based on IPv6.
JP-A No. 2007-104676 describes a VoIP (Voice Over Internet Protocol) terminal that has a message format conversion unit including a network interface for transmitting and receiving data to and from any terminal via a network. The message format conversion unit performs a format conversion of address information to an address format of any terminal, inserts the format-converted address information to a message and sends the message to the terminal. The message format conversion unit also performs a format conversion of address information included in a message received from any terminal to a predetermined address format and provides a message including the format-converted address information to a VoIP application.
According to the technology described in JP-A No. 2007-104676, regarding an application of VoIP having address information on Layer 7, it is possible to realize a communication between an IPv6 terminal and an IPv4 terminal in which applications operate.